Rich Hickey on Optionality, Schemas, and Clojure Spec

HN commenters send people to it whenever nulls, Maybe/Option or static typing come up, as a thoughtful dissent from the type-system orthodoxy that changes how some people model data.

Rich Hickey's Clojure/Conj 2018 keynote argues that Maybe/Option types and rigid type signatures are a poor way to model data that changes over time. He builds the case around optionality, schema growth and compatibility, and presents the ideas behind Clojure spec as an alternative.